Osteoglossum Bicirrhosum Research Articles

Identification of two effective sex-specific DNA markers in silver arowana (Osteoglossum bicirrhosum)

The silver arowana (Osteoglossum bicirrhosum), often referred to as a living fossil, presents significant challenges in sex identification based on morphological characteristics, with its sex determination mechanism remaining poorly understood. This issue poses considerable obstacles to its captive breeding efforts. Given the species' substantial value for both consumption and ornamental purposes, it is a critical candidate for aquaculture. Through genome sequencing, read mapping, and alignment analysis of five male and five female silver arowanas, along with one mixed pool of males, we successfully identified two sex-specific SNPs and confirmed a ZW model of sex determination in this ancient species. These two SNPs demonstrated remarkable accuracy, achieving 100 % success in genetic sex identification, as validated by Sanger sequencing of PCR products from 135 individuals. Both sex-specific SNPs are located approximately 26 kb upstream of the foxl2 gene, indicating a potentially pivotal role for the foxl2 gene in the sex-determination process of the silver arowana. Consequently, we have developed precise molecular markers for sex identification in the silver arowana, significantly enhancing reproductive efficiency and promoting further industrial development. This achievement lays a foundational basis for investigating the sex-determination mechanism of the silver arowana and other osteoglossid fish, thereby advancing aquaculture practices within this species.

Growth Performance of Silver Arowana Fed with Gryllus mitratus (Local Cricket) and Blaptica Dubia (Dubia Roach)

This research aimed to determine the feed types for Brazilian silver Arowana (Osteoglossum bicirrhosum), consisting of Poecilia reticulata (guppy fish), Gryllus mitratus (local cricket) and Blaptica Dubia (Dubia roach). The best feed ratios were compared to improve the performance growth of Arowana. The research was conducted in October - November 2022 at the ornamental fish farm named Badai Arwana Tasikmalaya, West Java. This research used an experimental method with a completely randomized design through five treatments and four repetitions. The treatments consisted of (A) guppy fish as the control feed (100%); (B) local cricket as the tested feed (100%); (C) Dubia roach as the tested feed (100%), (D) combination of guppy fish (50%) with local cricket (50%); and (E) combination of guppy fish (50%) with Dubia roach (50%). The treatments were given for 40 days, and the growth parameters of those Arowana seeds were then observed every 10 days. The observed parameters covered Survival Rate (SR), Absolute Length Growth (L), Absolute Weight Growth (W), Feed Conversion ratio (FCR), and Water Quality. SR, W, L, and FCR data were analyzed using ANOVA with a significant level of 95% and if there is a significant difference, the Duncan test will be further conducted. Meanwhile, water quality was descriptively analyzed.
 The research results showed that the feed combination of guppy fish (50%) with local cricket (50%) could improve the SR and growth performance of Arowana seeds. The given feed combination with the ratio of guppy fish (50%) with local cricket (50%) resulted in SR (100%), L (9.07 cm), W (10.53 g), and FCR (2.36). Meanwhile, the water quality during the research was in appropriate and stable conditions.

Phenotypic and genomic insights into the pathogenicity and antimicrobial resistance of an Enterobacter roggenkampii strain isolated from diseased silver arowana (Osteoglossum bicirrhosum).

Enterobacter roggenkampii is an opportunistic pathogen that causes infections in a wide range of hosts. A bacterial strain named EOBSR_19 was isolated from diseased silver arowana, Osteoglossum bicirrhosum. This bacterium was identified as E. roggenkampii based on the phenotypic characteristics and sequence analysis of the16S rDNA and gyrB genes. Average nucleotide identity and phylogenetic analysis based on the whole genome sequence further confirmed the bacterial taxonomy of EOBSR_19. Artificial experimental infection indicated that EOBSR_19 was pathogenic to fish. Antimicrobial susceptibility test showed it was multi-drug resistant. The EOBSR_19 was found to be resistant to 18 antibiotics belonging to quinolones, macrolides, sulfonamides, aminoglycosides, and β-lactams classes. The whole genome sequencing analysis showed that EOBSR_19 carried 730 virulence genes that were annotated for different functional modules, such as adhesion and invasion, secretion system, siderophore transport system and bacterial toxin. Among them, the virulence genes related to adhesion and invasion were the most abundant. In addition, drug resistance genes involved in multiple mechanisms of antimicrobial resistance were identified in its genomics, including multidrug resistance efflux pumps, antibiotic inactivating enzymes, and antibiotic binding site mutations. Its genomic analysis via whole-genome sequencing provided insights into the pathogenicity and antimicrobial resistance.

Silver Arowana

FisheriesVolume 48, Issue 3 p. 132-132 Backpage Silver Arowana First published: 27 March 2023 https://doi.org/10.1002/fsh.10898Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume48, Issue3March 2023Pages 132-132 RelatedInformation

Design of IoT Based Water Monitoring System (Simonair) For Arwana Fish Cultivation

Arwana fish is an ornamental fish that has high aesthetic value and is popular with Indonesian people. Silver Arowana is a type of freshwater ornamental fish originating from Brazil and belonging to the Osteoglossum genus. Problems in arowana fish farming include water quality, disease, nutrition and spawning (breeding). An important problem in enlarging silver arowana fish seeds is one of the maintenance media. Water quality is an external factor that plays a role in supporting fish growth. Water quality management has been one of the inhibiting factors in aquaculture, because it requires time, procedures and several stages to assess aquaculture water quality parameters, so farmers are late in handling the fish which results in death. Monitoring water quality that is practical, efficient and easy according to the development of IOT-based information technology 4.0 is urgently needed by cultivators to control fish in real time so that fish survival can be optimized. The research will be carried out for two years, namely 2022 and 2023. The purpose of the first phase of the research is to create an IOT-based Water Quality Monitoring System (SIMONAIR), while the second stage of research aims to apply the use of SIMONAIR to support the growth of arowana fish. The research was conducted at the Vocational School of IPB and in collaboration with a partner, namely CV Viez Aquatics. Phase 1 research will focus on the manufacture and calibration of SIMONAIR. Phase 2 research The use of the SIMONAIR application on silver arowana fish given different feed treatments. The overall research results are a technology package for silver arowana fish cultivation with high technology for the community or fish farmers

Design of IoT Based Water Monitoring System (Simonair) For Arwana Fish Cultivation

Arwana fish is an ornamental fish that has high aesthetic value and is popular with Indonesian people. Silver Arowana is a type of freshwater ornamental fish originating from Brazil and belonging to the Osteoglossum genus. Problems in arowana fish farming include water quality, disease, nutrition and spawning (breeding). An important problem in enlarging silver arowana fish seeds is one of the maintenance media. Water quality is an external factor that plays a role in supporting fish growth. Water quality management has been one of the inhibiting factors in aquaculture, because it requires time, procedures and several stages to assess aquaculture water quality parameters, so farmers are late in handling the fish which results in death. Monitoring water quality that is practical, efficient and easy according to the development of IOT-based information technology 4.0 is urgently needed by cultivators to control fish in real time so that fish survival can be optimized. The research will be carried out for two years, namely 2022 and 2023. The purpose of the first phase of the research is to create an IOT-based Water Quality Monitoring System (SIMONAIR), while the second stage of research aims to apply the use of SIMONAIR to support the growth of arowana fish. The research was conducted at the Vocational School of IPB and in collaboration with a partner, namely CV Viez Aquatics. Phase 1 research will focus on the manufacture and calibration of SIMONAIR. Phase 2 research The use of the SIMONAIR application on silver arowana fish given different feed treatments. The overall research results are a technology package for silver arowana fish cultivation with high technology for the community or fish farmers

Immuno-Enzymatic and Proteomic Approaches for Sexing the African Bonytongue (Heterotis niloticus Cuvier, 1829)

Heterotis niloticus is an African species of Osteoglossiformes that presents biological peculiarities and zootechnical performances favorable for fish farming. However, the absence of a sexual dimorphism hinders the optimization of its reproduction in captivity and limits the understanding of its reproductive behavior. This study is aimed at developing a minimally invasive and reliable sexing method to detect vitellogenin (Vtg) in female plasma. A commercial sexing kit (Acobium, Montpellier, France) for Arapaima gigas—a phylogenetically sister species of H. niloticus—successfully identified only 20% of mature H. niloticus females. Enzyme-linked immunosorbent assays (ELISA) were carried out using three Vtg antibodies. The A. gigas Vtg1 antibody cross-reacted significantly with plasma dilutions of female H. niloticus ranging from 1:1000 to 1:10,000, but with relatively low intensity. The Vtg antibody from Osteoglossum bicirrhosum, another species of Osteoglossiformes, showed non-specific binding with the Vtg of H. niloticus female plasma. Finally, an antibody for H. niloticus Vtg developed in this study allowed us to differentiate the two sexes with plasma coating dilutions ranging from 1:1000 to 1:10,000. The results of the assay were validated by a proteomic approach showing that Vtg-targeted mass spectrometry analysis of H. niloticus blood protein extracts could be used to accurately determine the presence of Vtg in the plasma of mature females. The final validation of the ELISA technique using the H. niloticus Vtg antibody was confirmed by visual sexing of a significant number of blood-sampled fish gonads; 100% of the fish were correctly sexed by the ELISA method.

TRAFFICKING OF ORNAMENTAL FISH IN THE BRAZILIAN AMAZON

The trafficking of ornamental fish is growing on a yearly basis in the Brazilian Amazon. This represents a serious threat to the biodiversity of the region. The objective of this research was to evaluate the trafficking of ornamental fish in the Brazilian Amazon using data from the seizures by the Federal Police and Brazilian Institute of Environment and Renewable Natural Resources - IBAMA. To assess and quantify this illegal trade, we gathered data relating to the period between January 2003 and January 2020. Information was obtained from IBAMA - Amazon - regional superintendence; National Amazon Research Institute - INPA regarding smuggled species that have been recovered and placed in its fish collection. The results show that in 98 seizures made by IBAMA, a total of 170,849 specimens of at least 73 species of 10 families, and 5 orders were recovered. Most of the illegally trafficked species are from the Loricariidae family (31 species, 8.47%). Hypancistrus zebra (Loricariidae), Potamotrygon jabuti, Potamotrygon leopoldi (Potamotrygonidae), Osteoglossum bicirrhosum and Osteoglossum ferreirai (Osteoglossidae) are the most targeted by the traffickers, due to their high value. At least 12 species are undescribed new species and were registered and placed in INPA’s fish collection. The fish followed different routes to reach the border that Brazil, Colombia, and Peru share. We conclude that in order to fight this illegal trade, tougher laws against smugglers, agreements with neighboring countries to combat trafficking, formal environmental education programs for riverine populations, and further scientific studies of smuggled species are necessary.

In vitro evaluation of natural hydroxyapatite from Osteoglossum bicirrhosum fish scales for biomedical application

AbstractThis study reports the obtainment of bioactive hydroxyapatite (HAp) extracted from scales of arowana fish (FSHA) (Osteoglossum bicirrhosum) by alkaline treatment followed by calcination at 600 and 800°C. The cell viability and bioactivity of hydroxyapatite particles (FSHA) were investigated and compared with those of HAp synthesized (s.HA) by the precipitation method. The HAp particles from fish scales showed non‐toxic behavior to dental pulp stem cells similar to HAp synthesized. Additionally, bioactivity assays show that the Hap from natural source forms the bone‐like apatite layer faster than s.HA sample, after being incubated in McCoy medium for 3 days. The results illustrate that HAp obtained from Osteoglossum bicirrhosum fish scale bio‐waste showed excellent biocompatibility. Besides, this study provides an effective method for converting low‐cost bio‐waste into a value‐added and it can be a potential alternative biomaterial for various biomedical applications.

Diversity of Balbiani body formation in internally and externally fertilizing representatives of Osteoglossiformes (Teleostei: Osteoglossomorpha).

During the early stages of oogenesis, the Balbiani body is formed in the primary oocytes. It consists of the Golgi apparatus, endoplasmic reticulum (ER), and numerous mitochondria aggregated with germ plasm, but its form may differ among animals. Hypothetically, during oogenesis oocytes become adapted to future development in two different environments depending on internal or external fertilization. We aimed to investigate, using light and transmission electron microscopy, the development of the Balbiani body during oogenesis in representatives of Osteoglossiformes, one of the most basal Teleostei groups. We analyzed the structure of oogonia and primary oocytes in the internally fertilizing butterflyfish Pantodon buchholzi and the externally fertilizing Osteoglossum bicirrhosum and Arapaima gigas to compare formation of the Balbiani body in relation to modes of fertilization. We demonstrated that the presence of the germ plasm as well as the fusion and fission of mitochondria are the conserved features of the Bb. However, each species exhibited also some peculiar features, including the presence of three types of ooplasm with different electron density and mitochondria-associated membranes in P. buchholzi; annulate lamellae, complexes of the Golgi apparatus, ER network, and lysosome-like bodies in O. bicirrhosum; as well as karmellae and whorls formed by the lamellae of the ER in A. gigas. Moreover, the form of the germ plasm observed in close contact with mitochondria differed between osteoglossiforms, with a "net-like" structure in P. buchholzi, the presence of numerous strings in O. bicirrhosum, and irregular accumulations in A. gigas. These unique features indicate that the extreme diversity of gamete structure observed so far only in the spermatozoa of osteoglossiforms is also characteristic for oocyte development in these basal teleosts. Possible reason of this variability is a period of about 150 million years of independent evolution of the lineages.

Ovary structure and oogenesis in internally and externally fertilizing Osteoglossiformes (Teleostei:Osteoglossomorpha)

AbstractIn this study, we assessed the ovary structure and early oogenesis in representatives of Osteoglossomorpha, one of the most basal Teleostei groups. We aimed to perform a comparative analysis between internally fertilizing Pantodon buchholzi (Pantodontidae) and externally fertilizing Osteoglossum bicirrhosum (Osteoglossidae), Marcusenius cyprinoides, Brevimyrus niger, Gnathonemus petersii and Mormyrus rume (Mormyridae). Our results indicated differences in ovary structure between P. buchholzi and the externally fertilizing species, as well as a considerable disparity in oocyte organization in all studied species. All species possess ovaries of the cystovarian type. In P. buchholzi, the epithelium lining the lumen was columnar and formed crypts with ciliated and microvillus cells as well as deep invaginations with secretory cells, whereas in the remaining species epithelium was squamous. The organization of oogonia and one‐nucleolus oocytes did not differ between species, there were variations in oocytes at subsequent steps of primary growth, including symmetry/asymmetry of the inner cell structure, differences in Balbiani body formation, presence/absence of zonation of the ooplasm, and differences in the order in which cortical alveoli and oil droplets appeared. These differences may be caused by a long and separate evolution of the families as well as adaptation to insemination in the family Pantodontidae.

The evaluation of seed production of silver arowana fish Osteoglossum bicirrhosum (Cuvier, 1829) with different natural feeding

Silver arowana fish, Osteoglossum bicirrhosum (Cuvier, 1829), is an ornamental fish originating from Brazil which has been popular among hobbyists. The increasing demand is not followed by an increase in fish production. To increase production, it is necessary to provide proper feed. The purpose of this study was to evaluate the production of arowana fish seeds by providing different natural feeds through growth and survival rate. This study was conducted using Completely Randomized Design (CRD). This study used 3 replications and 3 treatments (A: Tubifex sp., B: Chironomus sp., and C: combination of Tubifex sp. and Chironomus sp.). The length and weight results showed that treatment A had length of 0.45 cm, weight of 0.33 grams, treatment B had length of 3.36 cm, weight of 2.30 grams and treatment C had 1.65 cm, a weight of 1.28 grams. The survival rate showed that treatment A 60%,treatment B 100% and treatment C 67%. Based on these results, the natural feed of Chironomus sp. was very appropriate to increase the growth and survival rate of silver arowana fish seeds.

Aquarium trade and fish farms as a source of non-native freshwater fish introductions in French Guiana

Rivers of French Guiana are still little invaded by non-native fish, but several fish introductions were recently recorded through the development of aquarium fish trade and fish farms. Here we report records of 11 non-native fish species. Among them, four (Cichla monoculus,Heros efasciatus,Mesonauta guyanaeandPoecilia reticulata) are established and one of them (Heros efasciatus) is rapidly increasing its spatial range. Two species (Hyphessobrycon equesandPterophyllum scalare) were not retrieved in recent records and are probably extinct from French Guiana. The establishment status of the five other species (Arapaima gigas,Colossoma macropomum,Cyprinus carpio,Oreochromis mossambicusandOsteoglossum bicirrhosum) is uncertain and only a few specimens were observed in the wild. Nevertheless, these species, intensively reared in nearby countries, belong to highly invasive species able to cause detrimental impacts on recipient ecosystems. Those first occurrences of invasive fish species in French Guiana should therefore act as an early warning for both researchers and environmental managers.

Structural diversity of olfactory organs in Osteoglossiformes

AbstractOsteoglossomorpha, an ancient Teleostei group, exhibits many ancestral structural features. Herein, we describe the diversity in morphology of olfactory organs of air‐breathing Pantodon buchholzi, Arapaima gigas, and Gymnarchus niloticus in terms of adaptations to short ventures out of water and compare the results with the water‐breathing Osteoglossum bicirrhosum. We demonstrate the presence of olfactory rosettes within the olfactory chamber in all studied species and additionally a peculiar cudgel‐shaped structure in P. buchholzi. The typical olfactory rosette with centrally located elongate median raphe and two rows of olfactory lamellae was found only in P. buchholzi. In A. gigas, the olfactory lamellae arranged in semicircular manner were merged to small median raphe. Osteoglossum bicirrhosum and G. niloticus lacked median raphe, while the olfactory lamellae were ordered nearly parallel or circular, respectively. Olfactory epithelium lining the olfactory lamellae was unfolded only in P. buchholzi and G. niloticus. In contrast, in O. bicirrhosum and A. gigas convexities formed by nonsensory cells and concavities made by the sensory component were observed. Among the olfactory sensory neurons, ciliated and microvillus neurons were found in all studied species. Crypt‐like cells were noted only in P. buchholzi, whereas rod‐like cells were unique for A. gigas. The substantial morphological variation of the olfactory organ structure and ultrastructure in the studied osteoglossiforms may be explained by the early division of Osteoglossomorpha within Teleostei and long‐term, independent evolution within the families.

Isolation and molecular identification of Aeromonas species from the tank water of ornamental fishes.

Aeromonads are recognised as important pathogens of fishes. In this study, ten water samples were randomly collected from pet shops' fish tanks and home aquaria inhabited by several fish species (silver arowana, koi, goldfish, catfish, pictus fish, silver shark and silver dollar fish). Altogether 298 colonies were isolated using Aeromonas selective agar. A total of 154 isolates were then confirmed as belonging to the genus Aeromonas using the GCAT gene. Using ERIC-PCR, a total of 40 duplicate isolates were excluded from the study and 114 isolates were subjected to PCR-RFLP targeting the RNA polymerase sigma factor (rpoD) gene using lab-on-chip. A total of 13 different Aeromonas species were identified. The most prevalent species were A. veronii (27%, 31/114), followed by A. dhakensis (17%, 19/114), A. finlandiensis (9%, 10/114), A. caviae (8%, 9/114), A. hydrophila (4%, 4/114), A. jandaei (4%, 4/114), A. rivuli (3%, 3/114), A. enteropelogens (2%, 2/114), A. tecta (2%, 2/114), A. allosaccharophila (1%, 1/114), A. eucrenophila (1%, 1/114), A. media (1%, 1/114) and A. diversa (1%, 1/114). Twenty-six isolates (23%) were unidentifiable at species level. The present study demonstrates that Aeromonas species are highly diverse in freshwater fish tanks, and suggests the potential risks posed by the isolated bacteria to the health of ornamental fish species.

CRECIMIENTO Y SOBREVIVENCIA EN LA ALIMENTACION DE JUVENILES DE ARAHUANA Osteoglossum bicirrhosum

El objetivo del presente estudio fue evaluar el efecto de tres alimentos en el crecimiento y sobrevivencia de juveniles de arahuana Osteoglossum bicirrhosum. Se utilizaron 81 ejemplares (6,5 ± 0,36 cm y 1,03 ± 0,03 g) que fueron distribuidos en acuarios con 15 L de agua a densidad de 0,6 peces L-1. Se usaron tres alimentos: alimento balanceado comercial, quironómidos Chironomus sp. y ejemplares vivos de Poecilia reticulata, con tres replicas distribuidos en un diseño completamente al azar (DCA) durante 30 días. Los resultados muestran que los peces alimentados con quironómidos y alimento balanceado obtuvieron un desempeño significativo (p<0.05) en el peso, tasa de crecimiento especifico, tasa de crecimiento relativo y factor de condición en comparación con los juveniles alimentados con peces vivos. Sin embargo, no se encontró diferencias significativas (p>0.05) de longitud total y sobrevivencia en los diferentes tratamientos de alimentación. En conclusión el uso de quironomidos y alimento balanceado muestran un mejor desempeño en crecimiento en peso y factor de condición en los juveniles de arahuana O. bicirrhosum.

Interspecific Genetic Differences and Historical Demography in South American Arowanas (Osteoglossiformes, Osteoglossidae, Osteoglossum).

The South American arowanas (Osteoglossiformes, Osteoglossidae, Osteoglossum) are emblematic species widely distributed in the Amazon and surrounding basins. Arowana species are under strong anthropogenic pressure as they are extensively exploited for ornamental and food purposes. Until now, limited genetic and cytogenetic information has been available, with only a few studies reporting to their genetic diversity and population structure. In the present study, cytogenetic and DArTseq-derived single nucleotide polymorphism (SNP) data were used to investigate the genetic diversity of the two Osteoglossum species, the silver arowana O. bicirrhosum, and the black arowana O. ferreirai. Both species differ in their 2n (with 2n = 54 and 56 for O. ferreirai and O. bicirrhosum, respectively) and in the composition and distribution of their repetitive DNA content, consistent with their taxonomic status as different species. Our genetic dataset was coupled with contemporary and paleogeographic niche modeling, to develop concurrent demographic models that were tested against each other with a deep learning approach in O. bicirrhosum. Our genetic results reveal that O. bicirrhosum colonized the Tocantins-Araguaia basin from the Amazon basin about one million years ago. In addition, we highlighted a higher genetic diversity of O. bicirrhosum in the Amazon populations in comparison to those from the Tocantins-Araguaia basin.

WEIGHT-LENGTH RELATIONSHIP AND BLOOD CHARACTERISTICS OF SILVER AROWANA, A OSTEOGLOSSIDAE FROM THE STATE OF AMAPÁ (BRAZIL)

This study investigated the weight-length relationship, plasma biochemical and hematological parameters in Osteoglossum bicirrhosum from the Preto River, in the State of Amapá (Brazil). The weightlength relationship showed a negative allometric growth, with the value of the regression constant (b) equal to 2.539. The relative condition factor (1.00 ± 0.02) indicated good body conditions of fish in their natural environment. In the blood smears of O. bicirrhosum (616.2 ± 209.1 g), erythrocytes, thrombocytes and leukocytes were found with morphological characteristics similar to those of other Brazilian fish. Mean glucose levels were: 46.5 ± 14.6 mg dL-1 (27.1-95.8); total protein 4.2 ± 0.6 g dL-1 (2.3-5.3); total cholesterol 303.9 ± 140.4 mg dL-1 (81.6-718.4); triglycerides 244.8 ± 57.5 mg dL-1 (76.2-361.9); total erythrocytes 2.75 ± 0.37 x 106 μL-1 (1.940-3.350); hemoglobin 8.8 ± 1.2 g dL-1 (6.3- 13.0); hematocrit 26.6 ± 2.3% (21.0-32.0); mean corpuscular volume 98.6 ± 15.8 fL-1 (72.4-149.5); mean corpuscular hemoglobin concentration 32.9 ± 3.9 g dL-1 (23.4-44.8); total thrombocytes 90,816 ± 58,888 μL-1 (14,760-210,250); total leukocytes 75,287 ± 34,546 μL-1 (10,290-191,475); lymphocytes 72,555 ± 33,046 μL-1 (10,084-181,901) and 96.5 ± 2.5%(87-100); monocytes 1734 ± 1683 μL-1 (0- 7.308) and 2.3 ± 1.8% (0-7); neutrophils 915 ± 1435 μL-1 (0-6.518) and 1.1 ± 1.5% (0-7), eosinophils 63 ± 225 μL-1 (0-960) and 0.1 ± 0.3% (0-1). Therefore, lymphocytes were the predominant leukocytes, while eosinophils were the least frequent. This was the first report of leukocytes and biochemical parameters for O. bicirrhosum. Lastly, it was established reference blood values that can be used as interpretative data obtained for this species when under similar environmental conditions.

Length‐weight relationships of five fish species from lakes of the Central Amazonian floodplains

Parameters of the length‐weight relationship (LWR) were calculated for five fish species from Amazon Basin. Samplings were carried out in ten lakes of the Solimoes River floodplains during the four seasons of the hydrological cycle: rising water, high water, receding water, and low water, during two periods. The first period of eight years included samplings performed from 2001 to 2008 and the second sampling period of two years was from 2012 to 2013. Specimens were captured using gillnets (mesh sizes ranging from 30 to 120 mm between opposite knots) and standardized dimension of 20 m in length × 2 m in height. This study provides the LWR parameters for Acarichthys heckelii, Leporinus trifasciatus, Brycon amazonicus, Curimatella meyeri and Osteoglossum bicirrhosum.

ECTOPARÁSITOS ASOCIADOS A LAS BRANQUIAS DE LA ARAHUANA, Osteoglossum bicirrhosum (Cuvier, 1829) PROCEDENTES DE LA COCHA EL DORADO (RESERVA NACIONAL PACAYA SAMIRIA), AMAZONIA PERUANA

El objetivo de este estudio fue determinar la diversidad y abundancia de ectoparásitos en las branquias de 80 ejemplares de arahuana Osteoglossum bicirrhosum (Cuvier, 1829) provenientes del lago “El Dorado”, “Reserva Nacional Pacaya-Samiria”, Loreto, Perú. Las branquias de cada ejemplar fueron colectadas y colocadas por separado en solución formalina y agua (1:4000) y preservadas en refrigeración a 4°C hasta su análisis en el laboratorio. El análisis consistió en la localización, conteo, colecta y fijación de los ectoparásitos de cada arco branquial. Los resultados muestran que el 100% de los ejemplares analizados estuvieron infestados con uno o más ectoparásitos. Fueron identificados un total de cinco especies de Monogenoidea: Gonocleithrum cursitans Kritsky & Thatcher, 1983, Gonocleithrum aruanae Kritsky & Thatcher, 1983 y Gonocleithrum coenoideum Kritsky & Thatcher, 1983 y dos de Copepoda: Ergasilus sp. y Therodamas elongatus (Thatcher, 1986). Gonocleithrum cursitans fue el ectoparásito con mayor prevalencia (100%). Therodamas elongatus es reportado por primera vez en el Perú parasitando a ejemplares de O. bicirrhosum.